What Is Drug Used For?

Zinc sulfate is used systemically as a nutritional supplement in a variety of species. Oral zinc acetate has been shown to reduce copper toxicity in susceptible dog breeds (Bedlington Terriers, West Highland White Terriers) with hepatic copper toxicosis. Zinc therapy may also be of benefit in the treatment of hepatic fibrosis in the dog. Zinc sulfate is used topically as an astringent and as a weak antiseptic both for dermatologic and ophthalmic conditions.

When administered orally, large doses of zinc can inhibit the absorption of copper.

Pharmacokinetics

About 20-30% of dietary zinc is absorbed, principally from the duodenum and ileum. Bio availability is dependent upon the food in which it is present. Phytates can chelate zinc and form insoluble complexes in an alkaline pH. Zinc is stored mostly in red and white blood cells, but is also found in the muscle, skin, bone, retina, pancreas, liver, kidney, and prostate. Elimination is primarily via the feces, but some is also excreted by the kidneys and in sweat. Zinc found in feces maybe reabsorbed in the colon.

Before you take Drug

Contraindications / Precautions / Warnings

Zinc supplementation should be carefully considered before administering to patients with copper deficiency.

Adverse Effects

Large doses may cause GI disturbances. Hematologic abnormalities (usually hemolysis) may occur with large doses or serum levels greater than 1000 mcg/dL, particularly if a coexistent copper deficiency exists. Zinc acetate or methionine maybe less irritating to the stomach. Mixing the contents of the capsule with a small amount of tuna or hamburger may minimize vomiting.

Reproductive / Nursing Safety

Although zinc deficiency during pregnancy has been associated with adverse perinatal outcomes, other studies report no such occurrences. In humans, since zinc deficiency is very rare, the routine use of zinc supplementation during pregnancy is not recommended. In humans, the FDA categorizes this drug as category C for use during pregnancy (Animal studies have shown an adverse effect on the fetus, hut there are no adequate studies in humans; or there are no animal reproduction studies and no adequate studies in humans.)

Overdosage / Acute Toxicity

Signs associated with overdoses of zinc include hemolytic anemia, hypotension, jaundice, vomiting, and pulmonary edema. Suggestions for treatment of overdoses of oral zinc include removing the source, dilution with milk or water, and chelation therapy using edetate calcium disodium (Calcium EDTA). Refer to that monograph for possible doses and usage information.

Drug Interactions

The following drug interactions have either been reported or are theoretical in humans or animals receiving zinc and may be of significance in veterinary patients:

■ COPPER: Large doses of zinc can inhibit copper absorption in the intestine; if this interaction is not desired, separate copper and zinc supplements by at least two hours

How to use Drug

Drug dosage for dogs:

For adjunctive treatment and prophylaxis of hepatic copper toxicosis:

a) Initially, give a loading dose of 100 mg elemental zinc (zinc acetate used in this study) twice daily (separate doses by at least 8 hours) for about 3 months; then reduce dose to 50 mg (elemental zinc) twice daily. If animal vomits, give doses with a small piece of meat. Do not give within one hour of a meal. Monitoring of zinc levels every 2-3 months initially is recommended. Target zinc levels are 200-500 micrograms/ dl. Do not allow levels to increase higher than 1000 micrograms/dl. May require 3-6 months of therapy before significant efficacy is noted. ()

b) 5-10 mg/kg elemental zinc q12h; use high end of dosage range initially for 3 months, then 50 mg PO q12h for maintenance. Separate dosage from meals by 1 -2 hours. Zinc acetate or methionine maybe less irritating to the GI than other salts. Mixing the contents of the capsule with a small amount of tuna or hamburger may also minimize vomiting. In dogs with active copper-induced hepatitis, do not use zinc alone, but in combination with a chelator (g., D-penicillamine, trientine). Target zinc plasma levels >200 micrograms/dl but <400 micrograms/dl. Monitor levels every 2-3 months and adjust dosage as necessary. ()

Zinc sulfate occurs as a colorless granular powder, small needles, or transparent prisms. It is odorless but has an astringent metallic taste. 1.67 grams are soluble in one mL of water. Zinc sulfate is insoluble in alcohol and contains 23% zinc by weight (100 mg zinc sulfate = 23 mg elemental zinc).